黄河口潮间带碱蓬湿地植物-土壤系统V和Co生物累积的季节变化

2008年5—11月,对黄河口滨岸潮滩不同表现型碱蓬(Suaeda salsa)(中潮滩碱蓬,MMS,S.salsa in middle marsh;低潮滩碱蓬,LMS,S.salsa in low marsh)湿地植物-土壤系统V和Co含量的季节动态及其生物累积特征进行了研究。结果表明:MMS和LMS湿地表层土壤中V或Co含量的季节变化差异明显,但同一种湿地土壤中V和Co含量的变化模式相似。MMS(或LMS)湿地土壤的V含量均明显高于Co含量,二者在生长季的变异系数分别为12.01%、12.35%(MMS)和4.08%、4.94%(LMS)。MMS和LMS湿地表层土壤V的地累积指数(I_(geo))大多介于1—2,处于轻度污染状况;Co的I_(geo)大多介于0—1之间,处于无污染到轻度污染状态。V和Co含量在MMS不同部分中整体表现为枯落物根叶茎(P0.05),而在LMS中表现为枯落物叶茎根(P0.001)。MMS和LMS不同器官的V或Co转移能力存在较大差异,前者V和Co的R/S(根茎比)、R/L(根叶比)和S/L(茎叶比)大多大于1,后者中两种元素的相应比值则大多小于1。MMS和LMS不同部分的V和Co累积系数(AF)整体均表现为AFVAFCo,前者分别为后者的0.31—1.32、0.12—5.56、0.08—1.23、0.38—0.65倍(MMS)和0.14—0.84、0.23—0.68、0.34—0.77、0.43—0.56倍(LMS)。研究发现,MMS和LMS湿地土壤中有机质和铁锰氧化物含量的差异是导致二者V和Co含量存在差异的关键因素,而两种碱蓬生理生态学特性、所处生境水盐条件以及V和Co在不同器官扮演生态功能的差异是导致二者植物体内V和Co转移、分配与生物累积差异的重要原因。随着该区潮间带石油开采强度及石油燃料使用的增加,湿地表层土壤的V和Co(特别是V)污染问题将会逐渐凸显,而LMS可用于未来受V污染湿地修复的备选物种。

Seasonal variations of vanadium and cobalt bioaccumulation in plant-soil system of Suaeda salsa in the intertidal zone of the Yellow River Estuary

From May to November 2008, the seasonal variations of vanadium (V) and cobalt (Co) bioaccumulation of Suaeda salsa (S. salsa in middle marsh, MMS; S. salsa in low marsh, LMS) in the intertidal zone of the Yellow River Estuary were investigated. The results showed that the seasonal variations of V and Co contents in surface sediments of MMS and LMS were significantly different whereas those in the same marsh were similar. The V content in sediments of MMS or LMS was significantly higher than that of Co, and the coefficient of variations (CVs) during the growing season were 12.01%, 12.35% (MMS) and 4.08%, 4.94% (LMS), respectively. Geoaccumulation indices (I_geo) of V in surface sediments of MMS and LMS were mostly between 1 and 2, which could be classified as a moderately polluted level. The I_geo values of Co were mostly between 0 and 1, which could be classified as an unpolluted to moderately polluted level. The V and Co contents in different parts of MMS were generally in the order of litter > root > leaf > stem (P < 0.05), while those of LMS followed the order of litter > leaf > stem > root (P < 0.001). The transference of V and Co among different organs of MMS and LMS showed great difference. The R/S (root to stem), R/L (root to leaf), and S/L (stem to leaf) of V and Co in MMS were mostly greater than 1, whereas those in LMS were mostly less than 1. The accumulation factors (AF_s) of both V and Co in different parts (root, stem, leaf, and litter) of MMS and LMS showed AF_V > AF_Co, with the values being 0.31-1.32, 0.12-5.56, 0.08-1.23, and 0.38-0.65 times (MMS) and 0.14-0.84, 0.23-0.68, 0.34-0.77, and 0.43-0.56 times (LMS), respectively. The present study found that the differences of organic matter and Fe-Mn oxide contents in marsh sediments of MMS and LMS were the key factors resulting in the differences of their V and Co contents. Differences of the ecological and physiological characteristics, the water and salinity conditions in the habitat, and the ecological functions of V and Co between MMS and LMS showed significant influences on their transference, distribution, and bioaccumulation of the two elements. With increasing oil exploitation intensity and oil fuel usage, the V and Co (particularly for V) pollution in surface sediments of intertidal zone will be gradually highlighted, and the LMS can be used as the alternative species for marsh remediation resulting from V pollution.